Demographers studying the current population of a particular country produce the age-structure diagram shown in the figure below. The age ranges are listed in the center, and the population size is listed below the diagram.

Population pyramid for a country. The pyramids base shows that approximately 4 million males and 4 million females in the country are 0 to 5 years old. The next two levels of the pyramid are narrower; then the pyramid becomes wide again, representing approximately 4.2 million males and 4.2 million females between 15 to 20 years old. The pyramid reaches its widest point at the next level, which represents the men and women between 20 to 25 years old; it then becomes increasingly narrow before becoming wide again at the level that represents the men and women between 45 to 50 years old. The pyramid then becomes increasingly narrow; the levels for men become narrower than the levels for women.

Which of the following conclusions is supported by this diagram?

The birth rate has decreased during the past 10 years.
The largest age group is between 55 and 60 years old.
Significantly more females than males were born in the past 20 years.
There are nearly twice as many 70- to 74-year-old women than men in the same group.